The present invention generally relates to light curtains, and particularly relates to light curtain systems comprising multiple segments.
Light curtain systems are typically used to detect the intrusion of human limbs or other objects into hazardous areas, such the loading area of a hazardous machine. However, the range of light curtain uses extends into areas well beyond machine guarding, such as in work piece scanning, toll gate monitoring, and in other presence sensing operations.
A light curtain segment contains one or more light units. In a transmitter segment, the light unit comprises a light-emitting device, such as a diode. In receiver segments, light units comprise light receivers, such as photosensitive transistors or diodes. Typically, a transmitter segment includes a number of transmitting light units and a corresponding receiver segment includes a corresponding number of receiving light units. The spacing of light units within a segment largely defines the detection resolution of the segment, which establishes the minimum object size detectable by the light curtain.
Processing logic activates the transmitter""s light units, and monitors the receiver""s light units to determine whether or not the receiver receives light beams transmitted from the transmitter. Failure to receive one or more light beams generally indicates an obstruction in the plane between the transmitter and receiver segment. In many applications, the area to be monitored by the light curtain has a complex shape, or may be discontinuous, comprising several detection zones with potentially different detection resolution requirements.
Conventional approaches to providing light curtain monitoring in oddly shaped or discontinuous areas include the use of multiple light curtain systems. However, this approach may not be desirable in terms of efficiency, and because of the complications involved with interfacing independent light curtains into a machine control loop. Segmented light curtains based on a number of rigidly interconnected segments provide additional flexibility, as do ones based on flexibly interconnected segments. However, neither of these segmented approaches offers the needed configuration flexibility in many applications.
The present invention provides a method and systems to provide light curtain systems with enhanced configuration flexibility. A mixed architecture light curtain system comprises a mix of flexibly and rigidly interconnected light curtain segments. For example, a mixed architecture light curtain comprises a plurality of transmitter segments and a plurality of receiver segments, with each plurality comprising a mix of rigidly connected segments and flexibly interconnected segments that collectively form a group of interconnected segments. Thus, a mixed architecture light curtain preferably comprises a series of interconnected transmitter segments and corresponding series of interconnected receiver segments, where the inter-segment connections comprise a mix of rigid and flexible connectors.
With this approach, a portion of the light curtain may, for example, be based on rigidly interconnected segments, which allow the light curtain to conform to one or more perimeter angles, and may provide multiple planes of detection. This set of rigidly connected segments may then be connected through a flexible connector to an individual segment, which may itself be rigidly or flexibly connected to additional segments. Preferably, the rigid connectors and flexible connectors all provide for coupling of signals between the light curtain segments, such that the entire assemblage of interconnected segments, transmitter or receiver, functions as a series-connected set of segments.
xe2x80x9cRigid connectorxe2x80x9d used as a descriptive term herein encompasses a variety of connector configurations. The ""406 and ""098 patents incorporated herein by reference describe exemplary rigid connectors of various types, including both fixed-angle and rotatable-angle rigid connectors. These incorporated applications present exemplary embodiments of modular articulated light curtains, which comprise a series of light curtain segments interconnected by modular connectors that allow desired angular positioning of one segment relative to another, and permit the assembly of rigidly connected segments to conform to potentially complex detection perimeters. It should be understood that the present invention contemplates that one or more rigidly connected portions of a mixed architecture light curtain may comprise such modular articulated light curtains.
Rigid connectors may or may not include light units so as to continue detection capability across inter-segment junctures, and may or may not be configured to preserve beam spacing between joined segments. Nor is it necessary for a mixed architecture light curtain to maintain beam spacing across its collection of interconnected segments. Indeed, part of the mixed architecture""s flexibility derives from the ability to interconnect segments or groups of segments with potentially different beam resolutions.
The co-pending application entitled xe2x80x9cSegmented Light Curtain with Keyed Interfaces,xe2x80x9d also incorporated herein, illustrates the use of keyed rigid connectors to prevent misconnection between receiver and transmitter segments. Thus, rigid connectors as discussed herein may include keyed rigid connectors for differentiating between transmitter and receiver segments.
Keying may be extended to the flexible connectors, such that the flexible connectors configured for use with transmitter segments cannot be interfaced with receiver segments and vice versa. In general, the term xe2x80x9cflexible connectorxe2x80x9d as used herein provides an elongate, flexible interconnection between light curtain segments, providing freedom to independently orient the joined segments, while still providing for interconnection of one or more light curtains signals between the segments.
Preferably, the flexible connections comprise some type of connecting cable that carries one or more signals between interconnected light curtain segments. Many varieties of flexible connectors are contemplated, including those formed integrally into segments on one or both cable ends, and those formed with detachable connectors at one or both cable ends. As with the rigid connectors, a single mixed-architecture light curtain may include more than one type of flexible connector.
Of course, the present invention presents the opportunity for much variation. The following detailed description highlights many of the advantages and features of mixed architecture light curtains, and sets forth exemplary configurations. Other advantages, features, and desirable configurations will be apparent upon reading the description and examining the accompanying drawings.